Molecular pathology of tumor-initiating cells: Lessons from Philadelphia chromosome-positive leukemia

Prediction of Response to FDA-Approved Targeted Therapy and Immunotherapy in Acute Lymphoblastic Leukemia (ALL)

OPINION STATEMENT

Acute lymphoblastic leukemia (ALL) represents the predominant cancer in pediatric populations, though its occurrence in adults is relatively rare. Pre-treatment risk stratification is crucial for predicting prognosis. Important factors for assessment include patient age, white blood cell (WBC) count at diagnosis, extramedullary involvement, immunophenotype, and cytogenetic aberrations. Minimal residual disease (MRD), primarily assessed by flow cytometry following remission, plays a substantial role in guiding management plans. Over the past decade, significant advancements in ALL outcomes have been witnessed. Conventional chemotherapy has remarkably reduced mortality rates; however, its intensive nature raises safety concerns and has led to the emergence of treatment-resistant cases with recurrence of relapses. Consequently, The U.S. Food and Drug Administration (FDA) has approved several novel treatments for relapsed/refractory ALL due to their demonstrated efficacy, as indicated by improved complete remission and survival rates. These treatments include tyrosine kinase inhibitors (TKIs), the anti-CD19 monoclonal antibody blinatumomab, anti-CD22 inotuzumab ozogamicin, anti-CD20 rituximab, and chimeric antigen receptor (CAR) T-cell therapy. Identifying the variables that influence treatment decisions is a pressing necessity for tailoring therapy based on heterogeneous patient characteristics. Key predictive factors identified in various observational studies and clinical trials include prelymphodepletion disease burden, complex genetic abnormalities, and MRD. Furthermore, the development of serious adverse events following treatment could be anticipated through predictive models, allowing for appropriate prophylactic measures to be considered. The ultimate aim is to incorporate the concept of precision medicine in the field of ALL through valid prediction platform to facilitate the selection of the most suitable treatment approach.

Tyrosine Kinase Inhibitor Treatment for Newly Diagnosed Chronic Myeloid Leukemia

Chronic myeloid leukemia (CML) is a myeloproliferative disorder that accounts for approximately 10% of new cases of leukemia. The introduction of tyrosine kinase inhibitors has led to a reduction in mortalities. Thus, the estimated prevalence of CML is increasing. The National Comprehensive Cancer Network and the European Leukemia Net guidelines incorporate frequent molecular monitoring of the fusion BCR-ABL transcript to ensure that patients reach and keep treatment milestones. Most patients with CML are diagnosed in the chronic phase, and approximately 10% to 30% of these patients will at some time in their course meet definition criteria of resistance to imatinib.

Mechanistic / mammalian target protein of rapamycin signaling in hematopoietic stem cells and leukemia

Mechanistic/mammalian target protein of rapamycin (mTOR) is an evolutionarily conserved kinase that plays a critical role in sensing and responding to environmental determinants such as nutrient availability, energy sufficiency, stress, and growth factor concentration. mTOR participates in two complexes, designated mTOR complex 1 (mTORC1) and 2 (mTORC2), both of which phosphorylate multiple substrates. Recent studies have revealed that the fine-tuning activity of mTOR complexes contributes to both maintenance of hematopoietic stem cells (HSCs) and suppression of leukemogenesis. Dysregulation of mTORC1 activity results in impaired HSC homeostasis. Abnormalities of mTOR signaling are observed in many patients with leukemia and genetic studies clearly show that the leukemogenesis associated with Pten deficiency involves both mTORC1 and mTORC2. Although the several mTOR inhibitors have been developed for cancer therapy, effectiveness of the inhibitors for eradication of leukemia stem cells (LSCs) is unknown. Advances in understanding of how mTOR signaling is involved in mechanisms of normal HSC and LSC homeostasis may lead to novel therapeutic approaches that can successfully eradicate leukemia.

Cancer stem cell targeting: the next generation of cancer therapy and molecular imaging

Cancer stem cells (CSCs) have the capacity to generate the heterogeneous lineages of all cancer cells comprising a tumor and these populations of cells are likely to be more relevant in determining prognosis. However, these cells do not operate in isolation, but instead rely upon signals co-opted from their microenvironment, making the targeting and imaging of CSCs within a cancer mass a daunting task. A better understanding of the molecular cell biology underlying CSC pathology will facilitate the development of new therapeutic targets and novel strategies for the successful eradication of cancer. In addition, the continued investigation of sensitive molecular-imaging modalities will enable more accurate staging, treatment planning and the ability to monitor the effectiveness of CSC-targeted therapies in vivo. In this review, we explore the possibilities and limitations of CSC-directed therapies and molecular imaging modalities.